In this specification the term “drip tape” will be used to describe this precise product and also any other type of drip conduit, including those in round form more properly described as tubes or tubing. These terms are used interchangeably in this specification. All these products are made of organic plastic material, usually with thin walls. They include in their length a series of spaced-apart emitters.
Emitters are passages through the walls from the lumen of the tape to its outside. They permit controlled flow of water through the wall at their specific places along the length of the tape and allow water to flow through them at a limited rate into the soil on or in which the tape is laid or implanted. These provide for application of water in known amounts at precise locations relative to the crop, plant, or tree, thereby saving water that would otherwise be wasted if it were applied where it was not required by the crop.
Very frequently these tapes are laid along a row, which may be as long as 2500 feet, from a central source such as a manifold. A plurality of tapes usually extends from the manifold which acts as a header. At its upstream end, each tape must be connected to the manifold and depending on the layout, at its downstream end to a splice that connects it to a next-downstream length of the tape to extend the length of a tape completely along a row.
Also frequently there are breaks in the tape after it is installed, and a splice must be made at the point of breakage. This point generally occurs in a muddy and inconvenient location. There are other problems, especially when joining the tape to a next body such as a coupler. One prevalent frustration derives from the inherent construction of drip tapes, which are usually provided flattened and wound on a reel for storage. The material is an organic plastic with a relatively thin wall. It is flexible enough to expand to a rounded shape when filled with water under pressure, and elastic enough that it can be stretched to fit on and over part of a connector.
The thickness of the drip tape material is deliberately made as thin as possible to save material, to facilitate its storage and carriage and to facilitate its engagement to a coupler. In the construction of various types of tubular drip tape, an internal axially extending lip occurs along the length of the tape when the plastic sheet material is fused at its overlapping edges to form the tube. The radial thickness of the internal lip is greater then that of the non-overlapping portions of the tube wall and consequently to obtain a watertight seal the internal lip must be sufficiently compressed by the coupler without deforming or excessively decreasing wall thickness of the un-overlapped portion. One of the problems this presents is that excessive tightening of the coupler may cause the coupler to cut through the tape, thereby preventing the desired connection. An accompanying problem is under tightening, because then the joint will come apart in use when under pressure.
Coupling of the drip tape may have to be made under both dry and wet conditions and in clean and muddy environments. The workman who relies on feel alone or depends on previous experience as he assembles the coupler to the tape may be misled into making an insufficient or damaging joinder. It is desirable therefore to form a coupling joint by eliminating guesswork and forming the joint by reference to objective criteria.
This invention involves pressing a stiffly flexible tubing over a shouldered coupler end and then tightening a nut onto the coupler and against the tubing utilizing objective criteria to consistently position the nut, without cutting the tape, to form a water tight seal. In the field, to produce this result routinely is a surprisingly large order.